What are the best conditions for a successful negotiation?

By looking for the approval or consent of the counterparty in discussion and consultation. By causing the desired action and ultimately closing the case. What you absolutely need: 

1. Preparation and analysis.
2. Boundary investigation and determination.
3. Emotional distance and cold-bloodedness.
4. Listening comprehension.
5. Communication technology.
6. Timing and closing methodology. 
7. Training and coaching.

What do you definitely need to do beforehand during a negotiation to increase your chances of success? Find out: what your interests are. What is the interest of the other party. What is your and their vision, need and purpose. In the short, but certainly also in the long term. That you have a life, career or business plan that fits this. That you are working towards something, instead of moving away from something. That it fits in your / the bigger picture.